412 
BULLETIN OF THE BUREAU OF FISHERIES 
Whether the summer augmentation of C. tripos, accompanied as it is by a decrease 
on the part of C. longipes, actual as well as relative, originates as the result of local 
propagation of the few specimens that survive the spring, or from immigration from 
the south and west, or of both processes, is not yet clear; but in either case the central 
deeps may be looked upon as its chief area of multiplication in the Gulf of Maine. 
From this center it gradually expands its area of abundance right in to the immediate 
vicinity of the land where C. longipes decreases in abundance as the numbers of C. 
tripos augment, just as happens offshore. 
Relative abundance of the two 'predominant species of Ceratiuni, July and August, 1914 
Station 
C. lon- 
gipes 
C. tripos 
Station 
C. lon- 
gipes 
C. tripos 
10213 
50 
1 
10249 
13 
47 
10216 
38 
14 
10250. 
32 
2 
10223 
21 
1 
10251 
115 
1 
10225 
9 
4 
10253 
2 
10 
10227 
34 
1 
10254 
4 
50 
10229 
21 
1 
10255 
0 
50 
10230 
60 
0 
10256 
76 
10245 _ 
105 
2 
10258. 
1 
11 
10246 
62 
4 
10264 
1 
23 
10248 
29 
1 
C. tripos usually predominates near Cape Cod and in the southern part of Massa- 
chusetts Bay by the last week in August. For example, we found 23 tripos to 1 
longipes off the east side of Stellwagen Ledge on August 28, 1914 (station 10264), 
while the relationship between the two species was much the same near Provincetown 
on the 29th of the month in 1916 (station 10298). In some years, at least, this 
practical elimination of C. longipes from the catches happens equally early in the 
season near Cape Ann, where we found C. tripos much the more abundant of the 
two as early as August 22 in 1914 (station 10253, five times as many tripos as longipes), 
but in other summers C. longipes persists in numbers in the northeastern part of 
Massachusetts Bay long after tripos has taken its place off Cape Cod. This was 
the case in 1915, when the former predominated off Cape Ann on August 31 (station 
10306, 17 longipes to 2 tripos ) and about equaled tripos there as late as September 29 
(station 10320), though the latter abounded, with almost no longipes, inside Stell- 
wagen Ledge and near the tip of Cape Cod, only a few miles distant to the south, 
on the same day (stations 10221 and 10222). In fact, it was not until well into 
October that tripos finally replaced longipes at our standard station off Gloucester 
during that autumn (station 10330, October 18, 100+ tripos to 1 longipes). Prob- 
ably the fact that C. longipes may persist in abundance in the northern side of Massa- 
chusetts Bay long after it has dwindled almost to the vanishing point in the southern, 
and such variations as I have just recorded in the precise date when C. tripos 
replaces it off Cape Ann from summer to summer, are due to variations in the drift 
flowing southward past Cape Ann, which may be expected to bring a constant supply 
of C. longipes with it throughout the summer, for the latter continues predominant 
over C. tripos, or at the least is a large factor in the peridinian plankton of the 
more northerly and easterly parts of the coastal belt of the gulf until well into 
the autumn as follows : 
